Is 50 Million the New Million?

There have been a lot of hungry upstarts hitting the meaty milestone of 50 million lately.

Photo-sharing program Instagram just passed the 50-million-user mark.

Draw Something -- the Pictionary-like drawing game that led Zynga (Nasaq: ZNGA) to shell out at least $180 million to acquire its creator -- hit 50 million downloads.

Rovio's Angry Birds Space hit 50 million downloads in a little more than a month.

Social sharing darling Tumblr broke through 50 million blogs last month.

Two of Apple's (NAS: AAPL) university partners on iTunes U -- Stanford and Open University -- have hit 50 million downloads apiece of their free course content.

Obviously, 50 million is a big number in any capacity, but it's the speed that investors need to watch here. Instagram had just 30 million users a month ago! Draw Something hit its mark in a mere 50 days, only to be outdone by Angry Birds Space, breaking through the barrier just 35 days after its release.

This is important. The ability to win over masses so quickly these days shortens the time in which an industry can be disrupted.

Just as Instagram was accepting a $1 billion buyout offer from Facebook, Kodak was unloading its once-popular photo-sharing business on Shutterfly (NAS: SFLY) -- the lone bidder -- for a paltry $23.8 million.

Even disruptors get disrupted. Zynga had to shell out big bucks for Draw Something parent OMGPOP because it feared being upstaged by indie developers. Zynga continues to trade below its recent IPO price because investors realize it will have to be perpetually snatching up startups that are climbing in Apple's App Store listings.

The takeaway for today's investors is that they have to be more alert than ever. They also shouldn't overpay for ridiculous growth when something better may be merely a tech startup away.

Keep that in mind as you weigh the decision to buy into Facebook later this month at its lofty $100 billion valuation -- and beyond.

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